To capture dust in air for cleaning, an air cleaner is used. In recent years, an air conditioner has an air cleaning function is some cases. There are air cleaners of a filter type and of an electrical dust collection type which are appropriately selected or used in combination according to the property of target particles or the size of an apparatus. The electrical dust collection type is smaller in fluid resistance than that of the filter type and can collect particles having a small particle size having relatively high efficiency.
An electrical dust collector includes a charging part and a dust collecting part which are arranged on the upstream side and the downstream side of the flow of air (gas flow) respectively. The charging part has an ionizing wire (or a needle electrode) and a counter electrode to generates plasma. Charged particles in the plasma give electrical charges to the dust in the gas flow. The dust collecting part has a dust collecting electrode and a counter electrode, and traps the charged dust by the dust collecting electrode.
Since particulates (fine particles) in the atmosphere may affect human health, there is increasing interest in particulates having a small particle size in recent years. For example, there is concern about influence on health of fine particulates having a particle size of about 2.5 μm or less (PM2.5) and of finer particulates such as ultra-fine particles having a particle size of about 0.1 μm or less (PM0.1). Accordingly, an electrical dust collector capable of removing the finer particulates is demanded. To improve the collection efficiency of fine particles having a small particle size, increasing the number and density of dust collecting electrodes is effective but is likely to lead to lamer pressure loss as making the mesh of a filter finer. It is required to improve the collection efficiency of fine particles while suppressing as much as possible the increase in pressure loss.